In the construction of wheelchair frames, there are many interception points of tubes wherein a T-joint is required. Normally, T-joints are made by simply welding one end of a tube to a mid-portion of another tube to thereby define a stem and cross-portion. The problem is that the weakest point in the T-joint is the interception point between the stem and cross-piece where the weld takes place and this portion will normally fail before any other parts of the frame.
In an effort to solve the foregoing problem, T-joints have been made in such a manner as to provide in essence an integrally formed connection between the stem and cross-piece of the joint. For example, by providing a cruciform-shaped stamping having a main cross-piece portion with opposite edges from which laterally extend semi-cylindrical portions, the opposite edges of the main cross-piece portion can be brought together by rolling the cross-piece portion into a cylindrical shape, this motion automatically bringing the oppositely extending semi-cylindrical portions together to form a stem. The opposed edges brought together can then be welded, the weld line following a lateral line on the cross-piece and stem. Further pipe sections can then be welded to the opposite ends of the cross-piece and the free end of the stem to form a desired T-shaped frame.
T-joints made in the foregoing manner are stronger than the heretofore referred to type T-joints where the stem is simply welded to the central portion of the cross-piece. However, under prolonged strain, the T-joint can still fail at the interception point where the stresses and strains are concentrated.